Fiberglass reinforced resin grating structures are currently in vogue since the encapsulating resin is highly corrosion resistant, offers significantly high resistance to fire and may be used in environments where sparking will not be tolerated as for instance in the liquid hydrocarbon processing field or for decks in marine vessels and the like.
Where, such fiberglass grating has been manufactured by compression molding of right angle intersecting cross bars with appropriate glass fiber strands within the mold cavities to provide the necessary glass fiber reinforcement, the size of grating sections is relatively small due to the limitations on the size of compression mold and on the mechanism for laying up the reinforcing glass fibers, within the mold cavities.
Attempts have been made to alleviate this problem by manufacturing grating components such as longitudinal bars, cross bars and the like by a pultrusion process. Such a pultrusion process requires the pulling of reinforcement fibers through a liquid resin bath and into a heated shaping die. The molten resin thermostats within the die producing a continuous solid part. While these components have to a large degree cost advantages over the compression molded counterpart grating, problems are experienced in coupling the longitudinal bars or bearing bars.
In one known type of pultrusion formed fiberglass reinforced resin grating, sold under the trademark DURADEK by Aligned Fiber Composites of Chatfield Minnesota, a number of bearing bars, which may be from six inches to 240 inches in length and manufactured by pultrusion, are positioned side-by-side, parallel to each other and laterally spaced by several inches. Holes are predrilled through the sides of the bearing bars at longitudinally spaced positions and the grating is assembled by inserting standard cross tie rods through the aligned holes of respective bearing bar. The tie rods are of circular cross section and have a diameter on the order of that of the holes drilled or otherwise formed within the bearing bars. Suitable adhesives are employed for adhesively locking the tie rods to the bearing bars in the areas of intersection. Problems of hole alignment occur. Such gratings are costly due to the dimensional tolerances needed to ensure proper coupling between the tire rods and the bearing bars and the prealignment needed between the rods and holes, prior to rod insertion. Additionally, the holes are drilled through the sides of the bearing bar along the longitudinal center line measurably weakening the bearing bars and thus limiting the overall strength of the completed grating to resist torsion, bending and the like loads.
It is therefore a primary object of the present invention to provide an improved fiberglass reinforced molded resin grating of pultruded bearing bars and intersecting right angled cross bars coupled in a manner which minimizes the loss in strength of the grating due to the coupling between those components, wherein coupling is effected by mechanical deformation of the cross bar when coupled to the bearing bar and wherein, the deflection required of the cross bar is self-induced as a result of a mechanical locking of the cross bars to the bearing bar.